Amplifier



AMPLIFIER Filed Nov. 1. 1924 Irm/entor: lrvi n3 T: Byrn 8 5 H is Attovney.

Patented Apr. 10, 1928.

UNITED STATES PATENT OFFICE.

IRVING F. BYRNES, OF SCHENECTADY, NEW YORK, ASSIGNOR T0 GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

AMPLIFIER.

Application filed November My present invention relates to systems for amplifying small variable currents, such for example, as those produced in response to sound waves, and more particularly to means for controlling the amount of amplification produced by an amplifying system.

In the amplification of telephone currents, particularly where the amplified currents are to be employed for modulation of high frequency currents, it is desirable to have means for controlling the amount of amplification which is obtained by the amplifying apparatus.

It is also desirable to control the amount of amplification at frequent intervals during the rendition of a musical selection, or during the course of an address.

The object of my invention is to provide a means for controlling the amount of amplification at the will of the supervising operator without at the same time introducing objectionable noises when the apparatus is being adjusted.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, will best be understood by reference to the following description taken in connection with the ac companying drawing in which I have indicated diagrammatically a circuit arrangement whereby my invention may be carried into eifect.

I have indicated in the drawing an amplifying arrangement for amplifying the variable currents produced by means of a push-pull microphone 1. This microphone is connected in a circuit arrangement commonly known as a push-pull circuit. This circuit includes a source of direct current 2, which is connected to one contact at the microphone 1 and to the central point of a primary winding 3 of a transformer, the terminals of which are connected to the other two contacts of the, microphone 1. The transformer primary 3 supplies currents to a secondary winding 4, which is included in the grid circuit of a thermionic amplifier 5. The output or plate circuit of amplifiers 5 includes an outputtransformer 6 by means of which the amplified currents may be supplied to other amplifiers or to modulating devices, as desired.

In order to control the amount of amplification produced by amplifier 5 the primary 1, 1924. Serial No. 747,385.

winding 3 is shunted by an impedance which in the present case I have indicated as an adjustable resistance 7. This resistance is connected between two points which are at the same potential with respect to the direct current component of the source 2, and when the value of resistance 7 is adjusted no objectionable clicks will be produced in the circuit arrangement as would be the case if the resistance were connected between two points which were at a different potential with respect to the direct current component of the source. By a variation of the resistance '7 current flowing in the transformer primary 3 may be varied at will and thereby the current supplied from the output transformer 6 may be varied.

hile I have shown and described only one specific embodiment of my invention it will be apparent that many modifications in the circuit arrangement used and the form of apparatus employed may be made without departing from the scope of my invention as set forth in the appended claims.

that I claim as new and desire to secure by Letters Patent of the United States, is

1. The combination in an amplifying system of a push-pull circuit arrangement which includes a source of direct current, and means for producing variable currents from said source of direct current, and an impedance connected between two points in said circuit arrangement which are at the same potential with respect to the direct current component of the source but at different potentials with respect to the Variable cur rents.

2. The combination in an amplifying system of a push-pull circuit arrangement which includes a source of direct current and means for producing variable currents from said source of direct current, and a variable resistance connected between two points in said circuit arrangement which are at the same potential with respect to the direct current component of the source but at different potentials with respect to the variable currents.

3. The combination in an amplifying system of a push-pull circuit arrangement which includes a source of direct current and means for producing variable currents, a transformer primary included in said circuit arrangement by means of which variable currents may be supplied to another cir cuit, and an impedance connected between two points in said transformer primary which are at the same potential with respect to the direct current component of the source.

4. The combination in an amplifying sys tem of a push-pull circuit arrangement which includes a source of direct current and means for producing variable currents, a transformer primary included in said circuit arrangement by means of which variable currents may be supplied to another circuit, and a variable resistance connected between two points in said transformer primary which are at the same potential with respect to the direct current component of the source.

The combination in an amplifying system of a push-pull circuit arrangement which includes a source of direct current and means for producing variable currents, a transformer primary included in said circuit arrangement by means of which variable currents may be supplied to another circuit, and an adjustable impedance connected between the terminals of said transformer primary.

6. The combination in an amplifying system of a push-pull circuit arrangement which includes a source of direct current and means for producing variable currents, a transformer primary included in said circuit arrangement by means of which var1- able currents may be supplied to another circuit, and a variable resistance connected between the tern'iinals of said transformer primary.

7. The combination in an amplifying system of a push-pull microphone, a circuit arrangement connected thereto which includes a source of directcurrent and a transformer primary, and an impedance connected between two points in said transformer promary which are at the same potential with respect to the direct current component of the source.

8. The combinationin an amplifying system of a push pull microphone, a circuit arrangement connected thereto which includes a source of direct current and a transformer primary, and a variable resistance connected across the terminals of said transformer primary.

In witness whereof, I have hereunto set my hand this th day of October. 1924.

IRVING F. BYRNES. 

